In a tandem type color image forming apparatus of an intermediate transfer system, mostly, color printing is performed by driving development units of all colors in contact with an intermediate transfer belt, and monochrome printing is performed by stopping color (yellow (Y), magenta (M), and cyan (C)) development units separated from the intermediate transfer belt and letting only a black (K) development unit contact with the intermediate transfer belt, so as not to consume the life of the color (Y, M, and C) development units during the monochrome printing.
Also, proposed is an apparatus (e.g., see Patent Document 1) that allows individual color development units independently to separate from or contact with the intermediate transfer belt, for example, because two color printing of red and black does not use (Y) or (C), printing is performed by stopping the (Y) and (C) development units separated from the intermediate transfer belt and letting only the used (K) and (M) units contact with the intermediate transfer belt, so as not to consume the life of unused color development units.